Increasingly complex electronic systems require increasingly denser structures of integrated circuits, passive components, and other discrete elements. Typical two-dimensional structures, where the elements are laid out on a printed circuit board or similar structure are beginning to not meet the performance requirements of advanced electronic systems. Hence, three-dimensional structures are being used to provide the needed levels of electronic circuit integration. These three-dimensional structures generally comprise multiple layers of devices along with multiple layers of interconnects to provide electrical connections between the devices.
One approach for providing interconnects in a multiple layer structure is to bond semiconductor devices formed on a substrate (e.g., a first substrate) to semiconductor devices from another substrate (e.g., a second substrate). Such bonding can continue for several layers and expand vertically. Bonding typically occurs between a conductor on the first substrate to another conductor on the second substrate.
Such conductors may diffuse into dielectric material on one of the substrates, oxidize after the bonding of the two wafers together, and this may result in degraded line resistance, electromigration performance, line-line shorting through diffusion of the conductive metallization layers, and reduced device reliability.